PP7 Virus-like Particles as a Biotechnology Platform

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Keshavarz-Joud, Parisa
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https://hdl.handle.net/1853/77713
Abstract
Virus-like particles (VLPs) have found applications in and across many different fields, aided by their stability, capacity for large-scale production, ability for multivalent display of foreign molecules, and inherent immunogenicity. This dissertation explores the versatile utility of VLPs across three distinct areas. The first study investigates the assembly tolerance of engineered dimeric PP7 VLPs by incorporating randomized 15-mer peptide sequences into their progenitor capsid proteins. Using a library-based approach with two iterative rounds of selection, we identified inherent preferences for hydrophilic peptides and for negatively charged amino acids (Asp and Glu) while avoiding bulky and hydrophobic residues like Trp, Phe, Tyr, and Cys. This work led to a considerable expansion of unique assembly-competent VLP sequences, demonstrating the adaptability of PP7-based VLPs to genetic and chemical modifications. The second study examines the structural diversity of VLPs derived from Leviphage PP7, revealing a range of capsid assembly morphologies influenced by small changes in coat protein sequences. This structural plasticity, observed in both native and dimeric forms, suggests that self-assembling structures may naturally exhibit more variability than previously believed, highlighting their capacity to evolve. Lastly, we developed VLP-based vaccines to address emerging variants of SARS-CoV-2. By displaying key peptide sequences from the receptor binding domain (RBD) on VLPs and using them in a heterologous prime-boost regimen with recombinant RBD, we successfully elicited the generation of mutant-biased antibodies in BALB/c mice. This approach identified novel monoclonal antibodies with high affinities towards critical mutations in SARS-CoV-2 variants such as Alpha, Beta, Delta, and Omicron. Overall, these studies collectively demonstrate the broad potential of VLPs for assembly-based applications, structural diversity, and adaptive vaccine development to meet the challenges posed by evolving viral threats.
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2024-04-27
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